Fracture pull-type reinforcement method for rock mass at top of cavern

Abstract

The application discloses a method for reinforcing rock fissures on the top of a cavern, which comprises the following steps: step one, detecting the distribution and parameters of the fissures in the rock; step two, determining the position and size of the drilling hole; step three, before drilling, digging a hole on the surface of the rock on the top of the cavern at the drilling position to form an anchor head position; step four, arranging a drilling machine to drill the hole; step five, installing a tension anchor cable in the hole and applying prestress to the two ends of the tension anchor cable; step six, supporting a formwork at the outcrop position of the fissures on the top of the rock; step seven, injecting grout into the fissures through the grouting hole on the outer sleeve; and step eight, putting the excavated surface block of the cavern back to the anchor head position. The method applies prestress to the tension anchor cable, enhances the integrity of the rock on the top of the cavern, injects grout into the fissured rock through the outer sleeve, and bonds the grout with the rock after solidification, so that further weathering and cracking are avoided, the reinforcing capacity is stronger, the anchor head hole and the anchor cable hole are smaller, and the damage to the rock of the cavern is smaller.

Description

Technical Field

[0001] This invention relates to the field of cavern rock mass repair technology, and in particular to a method for tension reinforcement of rock mass fissures at the top of a cavern. Background Technology

[0002] In my country, a large number of cultural heritages exist within rock formations and caves, such as grottoes, which are carved and excavated into mountains, containing profound historical and cultural value. However, under the influence of natural and human factors, the rock formations within these caves can suffer from cracking and collapse, causing devastating damage to their landscape. Therefore, the protection and reinforcement of cave rock formations should be given due attention. Currently, the main methods for reinforcing cave rock formations include fissure grouting and anchor bolting. These methods are widely used in many cave rock formation reinforcement projects, especially in grout formations. However, for cases where the rock formation at the top of the cave is severely cracked, or even where the cracks extend to the surface, grouting not only fails to provide effective reinforcement but also increases pressure on the cracked rock, further widening the cracks. While anchor bolting can ensure the integrity of the rock formation, it cannot slow down the continued weathering and cracking of the cracks. Therefore, designing a reinforcement method that can both increase the integrity of the cracked rock formation and slow down the development of cracks is crucial. Summary of the Invention

[0003] This invention provides a method for tension reinforcement of rock fissures at the top of a cavern, which can both increase the integrity of the fissure rock mass and slow down the further development of rock fissures.

[0004] The method for tension reinforcement of rock fissures at the top of a cavern includes the following steps:

[0005] Step 1: Conduct preliminary detection of fracture distribution and parameters in the rock mass;

[0006] Step 2: Determine the drilling location and size based on the actual situation;

[0007] Step 3: Before drilling, excavate a hole in the rock surface at the top of the tunnel where drilling begins to form the anchor head area;

[0008] Step 4: Deploy the drilling rig to drill holes, and clean the holes after drilling is completed;

[0009] Step 5: Install the tie anchor cable in the borehole and apply a suitable range of prestress to both ends of the tie anchor cable;

[0010] Step Six: Support the formwork at the outcrop of the rock mass fissure at the top;

[0011] Step 7: Inject grout into the crack through the grouting holes on the outer sleeve. Record the grouting volume during the grouting process to ensure that the grout fills the crack.

[0012] Step 8: Reinstall the excavated surface blocks of the cavern back into the anchor head area to complete the rock mass reinforcement.

[0013] Furthermore, the aforementioned tie anchor cable includes an outer sleeve, an inner sleeve, and steel strands disposed inside the inner sleeve, with the outer sleeve disposed outside the inner sleeve.

[0014] Furthermore, the two ends of the aforementioned steel strand are fixed to the anchor head of the rock mass from the inside out by pads, washers, and anchors.

[0015] Furthermore, the aforementioned steel strands are dispersed in the inner sleeve through an isolation frame. They can be designed and replaced later according to the lifespan of the tie anchor cable and the development of rock mass fissures. Grease is added between the inner sleeve and the steel strands for anti-corrosion and lubrication.

[0016] Furthermore, the replacement of the aforementioned tie anchor cables is carried out one by one. Once an old cable is pulled out, a new cable is installed and tensioned. When replacing the old cable, the prestress of the tie anchor cable must be released first before the tie anchor cable is replaced.

[0017] Furthermore, a spacer with a stable spacing is provided between the outer sleeve and the inner sleeve. The spacer has ventilation holes and grouting holes, and the grouting holes are connected to grouting pipes.

[0018] Furthermore, the outer casing has through holes in its wall, through which grout is injected into the crack.

[0019] Furthermore, during the drilling process in step four above, if there is groundwater or karst caves in the rock mass, and the water volume is small, drainage should be carried out before construction. If the water volume is large, grouting with perforated pipes should be used for drilling. During construction, the grouting pressure should be controlled according to the actual project conditions to avoid affecting the rock mass of the cavern.

[0020] Furthermore, during step eight above, a waterproof layer is filled into the gaps when reassembling the excavated surface blocks of the cavern.

[0021] Furthermore, the grouting material used in step seven above is a retarded grout.

[0022] The present invention has the following beneficial effects:

[0023] (1) The present invention sets up tie anchors on the rock mass at the top of the cracked cavern and applies a certain prestress to the anchors so that force can be transmitted between multiple cracked rock masses, thereby enhancing the integrity of the rock mass.

[0024] (2) The present invention simultaneously injects retarding grout into the cracked rock mass fissure space. The retarding grout, which has a certain bonding effect, can bond the cracked rock mass into a whole and form an integral whole with the tie anchor cable.

[0025] (3) The present invention designs the anchor head in the rock mass during drilling, and the tie anchor cables and anchors are all located in the anchor head formed by the excavation, which ensures the aesthetics of the cavern surface landscape.

[0026] (4) The reinforcement method of the present invention is particularly suitable for the rock mass at the top of the cavern with visible cracks. For this type of rock mass, the reinforcement effect is good, the construction damage is small and the construction process is simple.

[0027] (5) The present invention adds grease between the inner sleeve and the anchor cable to play a role in corrosion prevention and lubrication, which extends the service life of the tie anchor cable. Furthermore, the anchor cable can be designed and replaced according to the development of rock mass fissures in the later stage, ensuring the safety of the cavern and facilitating the long-term protection and reinforcement of the cavern. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the reinforcement of fractured rock mass according to the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the tie anchor cable in this invention;

[0030] Figure 3 This is a schematic diagram of the cross-section of the tie anchor cable in this invention.

[0031] In the diagram: 10-Tie anchor cable; 101-Outer sleeve; 102-Inner sleeve; 103-Steel strand; 104-Anchor; 105-Washer; 106-Pan block; 107-Ventilation hole; 108-Grouting hole; 109-Isolation frame; 20-Anchor head chamber; 30-Crack. Detailed Implementation

[0032] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0033] refer to Figures 1 to 3 This invention provides a method for tension reinforcement of rock fissures at the top of a cavern, comprising the following steps:

[0034] Step 1: Conduct preliminary detection of fracture distribution and parameters in the rock mass;

[0035] Step 2: Determine the drilling location and size based on the actual situation;

[0036] Step 3: Before drilling, excavate a hole in the rock surface at the top of the tunnel where drilling begins to form the anchor head area 20;

[0037] Step 4: Deploy the drilling rig to drill holes, and clean the holes after drilling is completed; the hole diameter should not be too large during drilling to avoid further damage to the rock mass;

[0038] Step 5: Install the tie anchor cable 10 in the borehole and apply a suitable range of prestress to both ends of the tie anchor cable 10;

[0039] Step 6: Support the formwork at the outcrop of the top rock mass fissure 30;

[0040] Step 7: Inject grout into the crack 30 through the grouting hole 108 on the outer sleeve 101. Record the grouting volume during the grouting process to ensure that the grout fills the crack 30.

[0041] Step 8: Reinstall the excavated surface blocks of the cavern back into the anchor head 20 to complete the rock mass reinforcement.

[0042] In the above steps, the following points should be noted:

[0043] In step one, when detecting the distribution of fractures, a tape measure or caliper is used for measurement. For locations that are not visible to the naked eye, X-ray detection can be used to preliminarily determine the shape and distribution of the fracture space, and then formulate the drilling construction parameters for the next step.

[0044] In the third step of construction, it is necessary to reasonably control the excavation range to meet the construction requirements while minimizing the impact of construction on the rock mass.

[0045] In step four, during drilling, if groundwater or karst caves exist in the rock mass, and the water volume is small, drainage should be carried out before construction. If the water volume is large, a perforated grouting method should be used for drilling, with sealing occurring simultaneously to prevent continuous water seepage from damaging the cave rock mass. During construction, the grouting pressure should be controlled according to the actual project conditions to avoid impacting the cave rock mass. Simultaneously, the drilling location should be selected based on the principle that the borehole must penetrate the main fissures of the rock mass and be far away from areas with well-developed micro-fissures to avoid the formation of secondary fissures.

[0046] When cleaning the hole, a high-pressure air gun is used to blow away the debris inside the hole.

[0047] Step 5: Before applying prestress to the tie anchor cable 10, the tensioning prestress needs to be determined by comprehensively considering the stability of the rock mass at the top of the tunnel and the uniaxial compressive strength test value (the sample required for the compressive strength test is processed from the rock core obtained by drilling construction), so that the rock mass will not deform and crack, and can maintain its integrity.

[0048] Step 6: When setting up the support formwork, ventilation holes should be provided to prevent air from being trapped in the cracks during grouting. The support formwork can be made of wood or plastic.

[0049] Step seven, grouting, uses a retarded grout to ensure it doesn't solidify as it flows deeper into the fissures. To ensure the grout fills the fissures, atmospheric pressure or high-pressure grouting is selected based on the rock mass conditions. The grouting pressure is determined through testing, prioritizing the avoidance of damaging the cavern rock mass. Fly ash is preferred as the grouting material, with the addition of retarded gelling water to ensure the grout bonds to the rock mass after solidification, rather than merely serving a filling function.

[0050] Furthermore, recording the grout volume during grouting allows for comparison with the detected fracture space size, enabling adjustments to the grouting pressure and time, and providing valuable experience for similar rock mass reinforcement projects.

[0051] During step eight, when reinstalling the excavated surface blocks of the cavern, waterproof material is filled into the gaps to form a waterproof layer, which can effectively prevent rainwater from seeping into the cavern rock mass through the gaps and avoid further damage. Polyurethane foam can be used as the waterproof material, and the pressure needs to be controlled during spraying.

[0052] The tie anchor cable 10 used for reinforcement includes an outer sleeve 101, an inner sleeve 102, and a steel strand 103 disposed inside the inner sleeve 102. The outer sleeve 101 is disposed outside the inner sleeve 102.

[0053] The two ends of the steel strand 103 are fixed to the anchor head portion 20 of the rock mass from the inside to the outside through the pad 106, washer 105 and anchor 104.

[0054] The steel strands 103 are distributed in the inner sleeve 102 through the isolation frame 109. They can be designed and replaced later according to the service life of the tie anchor cable 10 and the development of rock mass fissures. Grease is added between the inner sleeve 102 and the steel strands 103 for anti-corrosion and lubrication. When the anchor cable needs to be replaced, the principle of replacement is adopted one by one. The old cable is pulled out and the new cable is installed in place for tensioning. When replacing, the anchor head is chiseled open to release the prestress of the anchor cable before the anchor cable is replaced.

[0055] A spacer is provided between the outer sleeve 101 and the inner sleeve 102. The spacer fixes the inner sleeve 102 inside the outer sleeve 101, ensuring that the distance between the two sleeves remains constant. The spacer is a circular plate structure, welded and fixed between the two sleeves. The spacer has a vent hole 107 and a grouting hole 108. The grouting hole 108 is connected to the grouting pipe for conveying grout, and the vent hole 107 is used to discharge air from inside the sleeve and the rock fissure 30 to balance the air pressure during grouting.

[0056] The outer casing 101 has through holes on its wall to deliver grout into the fissure 30. The location of the through holes is related to the location of the fissure. During installation, the through holes of the outer casing 101 are placed in sections that communicate with the space of the fissure 30. The placement of the through holes needs to be determined based on the detection and arrangement of the fissure 30. Therefore, the location of the through holes will vary depending on the location of the drilled holes in different fissures 30. In addition, the number of through holes on the outer casing 101 is also determined based on actual conditions, generally distributed around the perimeter of the outer casing 101 wall. For smaller fissures, fewer through holes may be required.

[0057] The reinforcement method of this invention applies prestress to the anchor cables, enhancing the integrity of the rock mass at the top of the cavern. Simultaneously, grout is injected into the cracked rock fissures using an outer casing. After solidification, the grout bonds with the rock mass, preventing further weathering and cracking. Compared to simple grouting reinforcement and anchor bolt reinforcement, the reinforcement method of this invention has stronger reinforcement capabilities, requires smaller anchor head holes and anchor cable drill holes, causes less damage to the cavern rock mass, and does not affect the aesthetics of the cavern surface landscape, making it highly practical.

[0058] The above description is merely a preferred embodiment of the present invention, and does not represent all possible forms of the present invention. The scope of protection of the present invention is not limited to such specific statements and embodiments. Various other modifications and improvements can be made based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and these modifications and improvements are still within the scope of protection of the present invention.

Claims

1. A method for tension reinforcement of rock fissures at the top of a cavern, characterized in that, Includes the following steps: Step 1: Conduct preliminary detection of fracture distribution and parameters in the rock mass; Step 2: Determine the drilling location and size based on the actual situation; Step 3: Before drilling, a hole is excavated on the surface of the rock mass at the top of the cavern at the drilling site to form the anchor head (20). Step 4: Deploy the drilling rig to drill holes, and clean the holes after drilling is completed; Step 5: Install the tie anchor cable (10) in the borehole and apply a suitable range of prestress to both ends of the tie anchor cable (10); The tie anchor cable (10) includes an outer sleeve (101), an inner sleeve (102), and a steel strand (103) disposed inside the inner sleeve (102). The outer sleeve (101) is disposed outside the inner sleeve (102). A spacer with a stable spacing is provided between the outer sleeve (101) and the inner sleeve (102). The spacer is provided with a vent hole (107) and a grouting hole (108). The grouting hole (108) is connected to a grouting pipe. Step 6: Support the formwork at the outcrop of the top rock mass fissure (30); Step 7: Grout into the crack (30) through the grouting hole (108), record the grouting volume during the grouting process, and ensure that the grout fills the crack (30); the outer sleeve (101) has a through hole on its wall, and grout is injected into the crack (30) through the through hole; Step 8: Reinstall the excavated surface blocks of the cavern back into the anchor head (20) to complete the rock mass reinforcement.

2. The method for tension reinforcement of rock fissures at the top of a cavern according to claim 1, characterized in that: The two ends of the steel strand (103) are fixed to the anchor head (20) of the rock mass from the inside to the outside by a pad (106), a washer (105) and an anchor (104).

3. The method for tension reinforcement of rock fissures at the top of a cavern according to claim 1, characterized in that: The steel strands (103) are distributed in the inner sleeve (102) through the isolation frame (109). They can be designed and replaced later according to the life of the tie anchor cable (10) and the development of rock mass fissures. Grease is added between the inner sleeve (102) and the steel strands (103) to play a role in corrosion prevention and lubrication.

4. The method for tension reinforcement of rock fissures at the top of a cavern according to claim 3, characterized in that: The replacement of the tie anchor cable (10) is carried out one by one. When an old cable is pulled out, a new cable is installed and tensioned. When replacing, the anchor head must be chiseled open to release the prestress of the tie anchor cable (10) before the tie anchor cable (10) is replaced.

5. The method for tension reinforcement of rock fissures at the top of a cavern according to claim 1, characterized in that: In the drilling process of step four, if there is groundwater or karst caves in the rock mass, and the water volume is small, drainage should be carried out first before construction. If the water volume is large, grouting with perforated pipes should be used for drilling. During construction, the grouting pressure should be controlled according to the actual project conditions to avoid affecting the rock mass of the cavern.

6. The method for tension reinforcement of rock fissures at the top of a cavern according to claim 1, characterized in that: During step eight, a waterproof layer is filled into the gaps when the excavated surface blocks of the cavern are reassembled.

7. The method for tension reinforcement of rock fissures at the top of a cavern according to any one of claims 1 to 6, characterized in that: The grouting material used in step seven is a retarded grout.

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